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Table 4 Heart Rate Variability (Frequency Domain and Time Domain Measures)a at Rest and During 15° HUT by diagnosis

From: Autonomic cardiovascular control in older patients with acute infection and delirium: a pilot study of orthostatic stress responses

Characteristic Rest 15° tilt Change after 15° tilt
Delirium, n = 5 No delirium, n = 9 Delirium, n = 5 No delirium, n = 9 Delirium, n = 5 No delirium, n = 9
Frequency Domain Measures
 PSD RRI 2400 174 6213 141 − 202 13
(350–30,075) (16–20,659) (148–22,462) (46–19,083) (−7612–8015) (− 1576–439)
 LFnuRRI 21 29 23†† 39 2 7
(11–62) (17–57) (9–65) (25–62) (− 28–4) (−14–16)
 HFnuRRI 79 71 77†† 61 −2 −7
(39–89) (43–83) (35–91) (38–75) (− 4–28) (− 16–14)
 LFabsRRI (ms2) 419 27 854 29 −44 12
(87–11,813) (5–5986) (27–11,579) (10–5943) (−234–860) (− 69–163)
 HFabsRRI (ms2) 1804 88 5267 39 1 4
(86–7371) (8–14,150) (87–9161) (12–11,365) (− 1150–7071) (− 2785–130)
 LF/HF ratio 0.3 0.4 0.3 0.5 0 0.1
(0.1–1.6) (0.2–1.3) (0.1–1.9) (0.3–1.4) (− 0.7–0.3) (− 0.5–0.8)
Time Domain Measures
 SDNN (ms) 51 25 36 22 −15 b 0
(27–227) (8–69) (17–174) (13–63) (− 54 - -5) (− 12–16)
 pNN50 (%) 11 1 9 2 −1 0
(3–68) (0–36) (0–86) (0–20) (− 10–18) (− 16–16)
 RMSSD (ms) 36 20 30 30 −9 8
(15–151) (7–75) (27–33) (19–43) (− 120–19) (−44–23)
  1. LFnuRRI and HFnuRRI = low frequency and high frequency power in normalized units; LF or HF/(Total Power-VFL(very low frequency) × 100; LFabsRRI and HFabsRRI = power in high frequency and low frequency range in absolute values, respectively; LF/HF = ratio low frequency power/high frequency power; SDNN = Standard Deviation of all NN intervals; pNN50 = NN50 count divided by the total number of all NN intervals; NN50 = number of interval differences of successive NN intervals greater than 50 ms; RMSSD = Root of the Mean of the Sum of Squares of Differences between adjacent NN intervals; NN intervals = normal-to-normal intervals; BRS = Baroreceptor reflex sensibility
  2. p = 0.06, Mann-Whitney test
  3. ††p = 0.08, compared with controls
  4. a Values are medians and total range obtained from registration during sequences of four minutes at rest, and after tilt to 15°. Change after 15° tilt is compared to resting values
  5. bp = 0.01, Mann-Whitney test